# AGENTS.md: Bevy game (Rust)

## Commands
- `cargo run` (dev uses the `dynamic_linking` feature if configured) · `cargo test` · `cargo clippy -- -D warnings` · `cargo fmt --check`
- Check `Cargo.toml` for the exact Bevy version before writing code; Bevy's APIs change between minor releases. Follow that version's migration guide, not older examples.

## ECS rules
- Group features into plugins (`impl Plugin for CombatPlugin`) registered in `main.rs`.
- Data lives in components (small structs with `#[derive(Component)]`); global data in `Resource`s. No game state in statics.
- Spawn with component bundles via required components (`#[require(Transform, Sprite)]`) instead of the deprecated `*Bundle` structs.
- Systems are small functions taking queries: `fn move_player(time: Res<Time>, mut q: Query<&mut Transform, With<Player>>)`. Use `delta_secs()`.
- Order with `.chain()`, `.before()/.after()`, or system sets; run conditionally with `run_if(in_state(GameState::Playing))`.
- Use `States` for menus/game/pause and `OnEnter`/`OnExit` schedules for setup/cleanup.
- Communicate between systems with events/messages or observers, not shared mutable resources everywhere.
- Use `Query::single()` style results and handle the error instead of panicking.
- Load assets via `AssetServer` handles once; don't reload per frame.

## Don't
Don't fight the borrow checker with `unsafe` or by cloning large data each frame; split the query or use `ParamSet`.